Optical device with cantilevered fiber array and method

ABSTRACT

A fiber alignment device comprises a base having at least one alignment groove, a stripped portion of an optical fiber positioned in the at least one alignment groove, where a terminal end of the fiber extends beyond at least one of an end face of the base, and an end face of a cover bonded to the base to secure the optical fiber between the base and the cover, where an end face of the cover and the end face of the base are substantially non-parallel.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Nos. 60/693,820; 60/693,847; and 60/693,851, each filed Jun.24, 2005. Each of these applications are incorporated by referenceherein in their entirety.

FIELD OF THE INVENTION

The present invention generally relates to a cantilevered fiber array(CFA). The CFA can be used with integrated planar waveguide devices,such as a planar lightwave circuit (PLC).

BACKGROUND OF THE INVENTION

The optical component industry is currently developing integrated planarwaveguide devices, incorporating one or more optical functions onto asingle component. An issue is the method of optically connecting to/fromthe integrated device. The current industry standard is to activelyalign a butt-joint connection between an optical fiber array and theoptical component. This method generally requires the use of expensiveequipment and can be relatively time consuming.

For example, direct fiber attachment can be used in an effort to reduceassembly cost while maintaining optical transmission quality.Manufacturers are attempting to place fiber alignment features directlyon the optical devices. Conventional approaches for fiber attachmentinclude “single fiber at a time” and mass fiber attachment.

Due to the small size and tight spacing, the “single fiber at a time”method requires delicate fixturing to individually position and thenhold all the fibers in place during bonding. Additionally, handlingindividual fibers would be time consuming.

For example, U.S. Pat. No. 6,859,588; U.S. Pat. No. 6,795,634; andUS2003/0142922 describe conventional fiber optic block structures andmethods of manufacture.

SUMMARY OF THE INVENTION

According to a first exemplary embodiment, a fiber alignment devicecomprises a base having at least one alignment groove, a strippedportion of an optical fiber positioned in the at least one alignmentgroove, where a terminal end of the fiber extends beyond at least one ofan end face of the base, and an end face of a cover bonded to the baseto secure the optical fiber between the base and the cover, where an endface of the cover and the end face of the base are substantiallynon-parallel. In one aspect, the terminal end of the fiber extendsbeyond the end face of the base. In another aspect, the fiber alignmentdevice can be configured where the cover end face extends beyond the endface of the base. In another aspect, the base end face extends beyondthe end face of the cover. In another aspect, the terminal end of thefiber extends at substantially the same distance from the cover end faceand the base end face. In yet another aspect, an interstitial adhesivelayer is disposed between the base and the cover.

In yet another aspect, the fiber alignment device can further include anadhesive fillet disposed on at least one of the cover end face and thebase end face. In another aspect, the base further includes a supportregion to support a non-stripped portion of the fiber. In anotheraspect, the cover further includes a support region.

In another aspect, the base further includes a plurality of alignmentgrooves spaced apart substantially in parallel to receive a plurality ofoptical fibers. In another aspect, the plurality of optical fibersextend from a fiber ribbon cable.

In another aspect, the fiber body extends above the first surface of thebase when the fiber is positioned in the alignment groove.

In another aspect, the surface of the cover disposed on the positionedfiber is substantially planar. In an alternative aspect, the surface ofthe cover disposed on the positioned fiber includes at least onealignment groove.

In another aspect, at least one of the cover and the base includes achannel formed in a direction transverse to the at least one alignmentgroove.

In another aspect, the base comprises one of silicon, quartz, andborosilicate glass. In another aspect, the cover comprises quartz. Inyet another aspect, the cover comprises fused silica.

In yet another aspect, at least one edge of the cover is chamfered.

In yet another embodiment, a fiber alignment device comprises a basehaving at least one alignment groove, a stripped portion of an opticalfiber positioned in the at least one alignment groove, where a terminalend of the fiber extends beyond an end face of the base, and a coverbonded to the base substrate securing the optical fiber between the basesubstrate and the cover, where a cover end face extends beyond the endface of the base.

In another aspect, the end face of the cover is proximate to the endface of the fiber.

In another aspect, the terminal end of the fiber extends beyond thecover.

In another aspect, the base further comprises a support region tosupport a non-stripped portion of the at least one fiber.

In another embodiment of the present invention, a fiber alignment devicecomprises a base having at least one alignment groove, a strippedportion of an optical fiber positioned in the at least one alignmentgroove, where a terminal end of the fiber extends beyond an end face ofthe base, and a cover bonded to a top surface of the base substratesecuring the optical fiber between the base and the cover, where thebase end face extends beyond the end face of the cover.

In another embodiment, an in-process structure for a fiber alignmentdevice comprises a base having at least one alignment groove, a strippedportion of an optical fiber positioned in the at least one alignmentgroove having a terminal end, and a cover bonded to the base securingthe optical fiber between the base and the cover, where at least one ofthe cover and the base has at least one transverse channel, orientedtransverse to the at least one alignment groove, and where at least oneof the cover and the base has at least one sacrificial region.

In another aspect, the transverse channel prevents the flow of anadhesive disposed between the cover and the base.

In another aspect, at least one transverse channel is a channel formedin both the cover and the base.

In another aspect, the transverse channel is oriented substantiallyperpendicular to the alignment groove.

In another aspect, the transverse channel is v-shaped in cross-section.

In another aspect, the transverse channel is substantially rectangularin cross-section.

In another aspect, the base further includes a plurality of alignmentgrooves spaced apart substantially in parallel to receive a plurality ofoptical fibers. In another aspect, the plurality of optical fibersextend from a fiber ribbon cable.

In another aspect, the fiber body extends above the first surface of thebase when the at least one fiber is positioned in the alignment groove.

In another aspect, the surface of the cover disposed on the positionedfiber is substantially planar. In an alternative aspect, the surface ofthe cover disposed on the positioned fiber includes at least onealignment groove.

In another aspect, the base comprises one of silicon, quartz, andborosilicate glass. In another aspect, the cover comprises fused silica.

In yet another aspect, an edge of the cover is chamfered.

In another embodiment of the present invention, a method of forming afiber alignment device comprises providing a base having at least onealignment groove formed in a first surface thereof, providing a cover,and forming a transverse channel, oriented transverse to the at leastone alignment groove, in at least one of the first surface of the baseand a first surface of the cover. The method further includes placing astripped potion of an optical fiber in the at least one alignmentgroove. The method further includes bonding the cover to the base tosecure the optical fiber between the first surface of the base and thefirst surface of the cover. The method further includes releasing aportion of at least one of the base and the cover at the transversechannel.

In another aspect, the method further comprises polishing a terminal endof the optical fiber. In another aspect, the polishing is performedprior to the releasing step.

In another aspect, the terminal end of the optical fiber is one of flatpolished, conically polished, angle polished and wedge polished.

In another aspect, after the releasing step, a terminal end of theoptical fiber extends beyond at least one of an end face of the coverand an end face of the base.

In another aspect, after the releasing step, a terminal end of theoptical fiber extends beyond both end faces of the cover and base.

In another aspect, the releasing step comprises applying a force to atleast one of a sacrificial region of the base and a sacrificial regionof the cover, where the direction of the force is transverse to at leastone of the plane of the base and the plane of the cover.

In another aspect, the base further comprises a support region formed inthe first surface of the base.

In another aspect, the method further includes applying an adhesive tothe support region to secure at least one nonstripped portion of anoptical fiber.

In another aspect, the formation of the transverse channel comprises oneof a cutting process, an etching process and a grinding process.

In another embodiment, a method of forming a plurality of fiberalignment devices comprises providing a base having an array of baseportions wherein each of the base portions has at least one alignmentgroove on a first surface of the base. The method further includesforming a transverse channel in the base, where the transverse channelis oriented transverse to the at least one alignment groove. The methodfurther includes placing a stripped potion of an optical fiber in the atleast one alignment groove in each of the base portions. The methodfurther includes bonding a cover on the top surface of the basesubstrate to secure the at least one optical fiber between the base andthe cover. The method further includes singulating the base to form thealignment devices and removing a sacrificial portion of at least one ofthe base and the cover.

In another aspect, each of the base portions further comprise a stressrelief region formed in the first surface of the base.

In another aspect, the method further includes polishing the terminalends of the optical fibers prior to the removing step.

In another aspect, the terminal ends of the optical fibers are formed byone of flat polishing, conical polishing, angle polishing and wedgepolishing.

In another embodiment, a method of forming a fiber alignment devicecomprises preparing an optical fiber cable that includes a plurality offibers, wherein the preparing step comprises at least one of coiling,stripping and cleaving one or more of the fibers of the optical fibercable. The method further includes preparing a base to receive theprepared optical fiber, wherein the preparing step further includesforming a plurality of alignment grooves on a first surface of the base.The preparing step can further include forming a strain-relief region inthe base. The preparing step can further include forming a transversechannel in the base, where the transverse channel is oriented transverseto the alignment grooves. The method further comprises providing acover. The cover may include a substantially planar inner surface andmay further include a transverse channel formed in the substantiallyplanar inner surface.

The method can further comprise placing stripped portions of the fibersfrom the optical fiber cable in the plurality of alignment grooves andnon-stripped portions of the fibers in the strain-relief region. Themethod can further include aligning the cover to the fiber-filled base.The method can further include bonding the fiber-filled base to thecover to form an in-process fiber array structure. A structural adhesivecan be used to bond the fibers to the base and cover.

The method can further include at least one of grinding and polishing aterminal end of the in-process fiber array structure. The polishingprovides at least one of flat-polished, wedge-polished, cone-polished,or angle-polished terminal ends of the fibers. The method furtherincludes releasing the fibers from at least one of a sacrificial portionof the cover and a sacrificial portion of the base. The method canfurther include cleaning the released fibers.

The above summary of the present invention is not intended to describeeach illustrated embodiment or every implementation of the presentinvention. The figures and the detailed description that follows moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an exemplary cantilevered fiber array.

FIGS. 2A-2F show side views of alternative exemplary configurations of acantilevered fiber array.

FIG. 3A shows a side view of an exemplary in-process fiber arraystructure.

FIG. 3B shows three example base configurations for an in-process fiberarray structure.

FIG. 4 is a flowchart showing an exemplary method of making acantilevered fiber array.

FIG. 5A shows a side view of an exemplary CFA-PLC device.

FIG. 5B shows a top view of CFAs and PLCs produced in mass form,including non-diced CFA strips and a non-diced PLC strip.

FIG. 6 is an isometric view of an exemplary PLC.

FIG. 7A shows an isometric view of an alternative CFA device. FIG. 7Bshows an isometric exploded view of the alternative CFA device of FIG.7A.

FIG. 8 shows an isometric view of a PLC device configured as a sensor.

FIG. 9 shows an isometric view of an alternative CFA-PLC device.

FIGS. 10A and 10B show an isometric and an exploded view of analternative CFA plug-type element.

FIGS. 11A-11E show views of a connection sequence of the CFA-PLC deviceof FIG. 9.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following Description, reference is made to the accompanyingdrawings which form a part hereof, and in which are shown by way ofillustration specific embodiments in which the invention may bepracticed. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the figure(s) being described. Becausecomponents of the embodiments of the present invention can be positionedin a number of different orientations, the directional terminology isused for purposes of illustration and is not limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention.

An embodiment of the present invention generally relates to a devicereferred to as a cantilevered fiber array (CFA). The CFA can be used tocouple with planar waveguide devices, such as a planar lightwave circuit(PLC). The description also provides a method to produce, assemble andpolish CFAs, which can provide a mechanism to passively perform masstermination directly to optical components. The description alsoprovides mechanisms to facilitate automated assembly and machinehandling of (many) fiber wide arrays. The description also provides amethod to passively couple one or more CFAs to a PLC.

As shown in isometric view in FIG. 1, an exemplary CFA 100 includes oneor more fibers 110, such as from an optical fiber cable, such as a fiberribbon cable 115. Stripped portions of the fibers are mounted on a baseor substrate 120 (also referred to herein as a base substrate). Thesubstrate 120 includes a plurality of fiber guides or channels 125, suchas v-grooves, in which stripped portions of the fibers 110 are disposedand guided. A cover 130 can be optionally disposed on thesubstrate/guided fibers to prevent fiber displacement within thechannels or grooves and to provide additional support. In addition, anadhesive (see FIGS. 2A-2F), such as a structural adhesive (e.g., athermally accelerated or thermally curable structural adhesive, (e.g., atwo-part epoxy, or the like)), can be provided to bond the fibers to thesubstrate 120 and guides 125, and to bond the cover 130 to the substrate120. As shown in FIG. 1, a relatively thin adhesive layer 140 can beformed between cover 130 and substrate 120. Methods of forming the CFAand of coupling the CFA to a PLC are described in further detail below.

The base or substrate 120 provides support for the stripped andnon-stripped portions of the fibers being aligned. An exemplary base orsubstrate 120 material is Silicon (Si), with a crystal orientation of[100], which provides for v-grooves to be accurately formed using theconventional Si photolithography infrastructure. Other materials (e.g.quartz, fused silica, borosilicate glass, etc.) can also be utilized.For example, fused silica provides essentially the same chemical,mechanical and thermal characteristics as the fibers being aligned. Inthe exemplary embodiments, conventional silica-based telecommunicationsfibers, such as 125 μm outer diameter (OD) SMF-28 Photonic opticalfibers, commercially available from Corning Inc. (Corning, N.Y.), areutilized. As would be apparent to one of ordinary skill in the art, manydifferent types of conventional optical fibers of differing ODs can beutilized in accordance with the embodiments described herein.

An exemplary cover 130 material is silica-based, such as fused silica orquartz, which nearly matches the chemical, mechanical and thermalcharacteristics of the guided fibers. Also, the chemicals used to cleanthe fibers can also be employed on the cover without leaving any type ofresidue on the fiber. A fused silica cover can be cut using the sameequipment used with Si wafers. During the grinding/polishing operations,as explained in more detail below, a fused silica cover material isremoved cleanly without coating the fibers. In addition, a fused silicacover can be transparent to ultraviolet (UV) light, which allows the useof an exemplary UV initiated, thermally cured index matching opticaladhesive when bonding the CFA to a waveguide device, such as a PLC. Forexample, an adhesive such as Optodyne™ UV-2100 or UV-3100, availablefrom Daikin Industries, Ltd, of Osaka Japan, can be utilized. Suitableadhesives are also described in commonly-owned, co-pending U.S. patentapplication Ser. No. 11/423,191 (Attorney Docket No. 61993US002),incorporated by reference herein in its entirety. In alternativeembodiments, a material such as a silicon or another silica-basedmaterial can be used to form cover 130.

In addition, the adhesive layer 140 can be formed using a structuraladhesive, such as a thermally cured or a thermally accelerated epoxy.For example, an adhesive such as 3M DP-190 Scotch-Weld adhesive,available from 3M Company, St. Paul, Minn., can be utilized. Further,other types of adhesives can be employed, depending on the bonding andmechanical properties that are appropriate for the base and covermaterials.

More detailed views of several exemplary embodiments are shown in sideview in FIGS. 2A-2F. Although only one fiber is shown in each of theseexemplary embodiments, each CFA embodiment may incorporate one or morefibers, depending on the desired application.

The CFA 200A of FIG. 2A includes a base or substrate 220, similar tobase or substrate 120 described above. The base or substrate 220includes a fiber support region 225 and a fiber guiding region 226,which includes fiber guiding channels, such as v-grooves. The number ofv-grooves located in fiber guiding region 226 can be the same as orgreater than the number of fibers being aligned. The fiber supportingregion 225 supports the non-stripped portion of fibers 210, whereasstripped portions of the fibers can be disposed in the channels formedin fiber guiding region 226. The “stripped” portions 212 of fibers 210refers to the core/clad light-guiding portions of the fibers, which mayhave one or more protective buffer coatings removed to expose the glasscore/clad of the fiber. The fiber is “cantilevered” in that its terminalend extends beyond one or both end faces 223, 233.

An adhesive 240, such as a thermally curable adhesive, can be disposedon the base or substrate 220 to bond the fibers to the support. Theadhesive is also used to bond the optional cover 230 to the base orsubstrate 220. Although cover 230 is shown as having a generallyplanar/flat structure, in an alternative aspect, cover 230 can beconfigured to include a support region, similar to region 225 of base orsubstrate 220. Based on the structure of the in-process device(described below) that is used to form CFA 200A, an adhesive fillet 242is also formed at the end face of either the base-substrate or thecover, or both. The adhesive fillet 242 can provide a strain-reliefmechanism, i.e., a “slow” migration from the little/no supportcantilevered region, to a fully supported region between the base andcover.

In addition, as shown in FIG. 2A, and as described in more detail below,the end face 223 of the base substrate and the end face 233 of the coverare non-parallel. Also, the fiber terminal end(s) 213, which can beflat-polished, wedge-polished, cone-polished, or angle-polished,extend(s) beyond the end faces 223, 233 in this configuration.

In the embodiment of FIG. 2A, the end faces 223, 233 are proximate toeach other with respect to the extending fiber (i.e., the end faces 223,233 are about the same distance from the terminal end 213 of thecantilevered fiber). In a different embodiment, as shown in FIG. 2B, CFA200B includes a cover 230 whose end face 234 extends to the terminal end213 of the fiber. In this embodiment, the cover extending to theterminal end of the fiber can minimize potential positional changes ofthe fiber caused by internal stress in the optical adhesive used to bondthe CFA to a PLC. In this embodiment, cover end face 234 can be polishedflat, angle-polished, conically polished, or wedge polished, while baseend face 223 is angled.

In a further embodiment, as shown in FIG. 2C, the cover 230 of CFA 200Cis truncated, such that the end face 223 of the base substrate extends agreater distance along the fiber than does the end face 233 of thecover. In yet another embodiment, as shown in FIG. 2D, the end face 233of the cover 230 of CFA 200D extends along the fiber at a greaterdistance than the end face 223 of the base substrate.

In a further embodiment, as shown in FIG. 2E, the cover 230 can extendbeyond the terminal end 213 of the stripped fiber. In anotherembodiment, as shown in FIG. 2F, the CFA includes a base or substrate220 that extends beyond the terminal end 213 of the stripped fiber.

In addition, in each of the embodiments of FIGS. 2A-2F, the base/coverend faces 223, 233 are non-parallel.

In an alternative embodiment (not shown), the cover 230 is absent, as astructural adhesive is used to bond the fibers in place in the grooveregion 226.

According to another embodiment, CFA's 100, and 200A-200F can bemanufactured in a straightforward method. For example, FIG. 3A shows anexemplary in process structure 300 that can be used to manufacturedifferent configurations of CFAs. FIG. 4 shows a flow chart 400 ofmethod steps that can be utilized in the manufacturing process.

In step 402, the fiber is prepared. Fiber preparation involves coiling,stripping, cleaning and/or cleaving individual optical fiber cables orcleaning, stripping, and/or cleaving individual fibers in a fiber ribboncable. In this step, the cable can be cut to a length that isapplication specific—for example, the fiber can be cut to lengths fromseveral millimeters to hundreds of meters in length. Coiling the fibercable can protect the fiber from handling damage during manufacturingand makes fiber management much more straightforward. One free end ofthe coiled fiber cable is then stripped, cleaved and cleaned. Fiberstripping can be accomplished using conventional techniques, such aschemical and/or mechanical techniques. The cantilevered fibers can thenbe cleaved to a length equal to the length of the base substrate (minusthe cable jacket strain-relief overlap). As part of the fiberpreparation, prior to placing the fibers into the guiding or v-groovesof the substrate, the fibers can be cleaned using a diluted potassiumhydroxide bath followed by series of deionized water rinses and drying.

In step 404, the base and cover substrates are manufactured. Asmentioned above, the base substrate provides support for the strippedand non-stripped portions of the fibers being aligned. An exemplary basesubstrate material is Silicon (Si), with a crystal orientation of [100],which provides for channels, such as v-grooves, to be accurately formedusing the conventional Si photolithography infrastructure. Othermaterials (e.g. quartz, fused silica, borosilicate glass, etc.) can alsobe utilized. For example, fused silica provides nearly the samechemical, mechanical and thermal characteristics as the fibers beingaligned. Other substrate materials (e.g., quartz) can be fabricated bygrinding, drawing or formed using other techniques.

Strips of multiple base portions or substrates can be used duringassembly to decrease overall assembly time. Base substrate strips caninclude base substrate sections corresponding to multiple CFAs. Basesubstrate thicknesses can range from about 100 μm to about 500 μm, forexample, with base widths being configured to be wide enough to supportfibers from a particular fiber ribbon cable (e.g., 4 fibers wide, 8fibers wide, 12 fibers wide, etc.) or from a plurality of fiber ribboncables. The length of the base substrate is selected to be long enoughto support both non-stripped portions of the fibers and strippedportions of the fibers.

Exemplary base substrates made out of silicon wafers can be fabricatedusing conventional photolithographic techniques to form the basesubstrate structure of the CFA. For example, as shown in the explodedside view of FIG. 3A, in process CFA structure 300, includes a basesubstrate 320, which is fabricated to include four main areas:strain-relief/fiber support region 325, fiber guide channel region 326,sacrificial portion or region 329, and a transverse channel portion 328,referred to herein as a “snap-gap.”

The CFA base substrate strain-relief region 325 provides clearance forthe thicker jacketed fibers 310 to allow the fibers to lay flat in thefiber guiding channels of region 326 without any abrupt bends in thefiber. Such clearance can be accomplished by forming a strain reliefregion as a recessed portion of the base. In addition, strain-reliefregion 325 provides a bonding area to adhere the optical fiber cablejacket to the base substrate. On a Si-based substrate, the strain-reliefregion 325 can be formed using a conventional etching technique, andalso at the same time as the guiding channels, such as v-grooves, andthe “snap-gap” are etched.

The CFA fiber guiding channel region 326 is the portion of the basesubstrate 320 that contains an appropriate number of channels orv-grooves that are formed on the correct center-to-center spacing tomatch a receiving PLC device channel spacing. The stripped optical fiberis guided and bonded into the base substrate channels in this region.For example, v-grooves spaced by an approximately 127 μmcenter-to-center spacing can be utilized to generate a CFA of compactwidth. Other center-to-center spacings can be utilized depending on theapplication and the type of PLC ultimately being coupled.

The shape and depth of the guiding channels can be formed through theuse of conventional etching techniques, such as a KOH anisotropic etchthrough a pre-patterned Si₃N₄ layer of the exemplary silicon substrate.

In an exemplary embodiment, the depth of the v-groove channels can beformed based on the diameter of the stripped optical fiber and to setthe gap or distance between the base 320 and the cover 330. The heightof the base/cover gap (e.g., between about 10 μm and about 70 μm, and insome cases about 40-55 μm) is set to reduce the amount of adhesiveutilized while increasing the base/cover adhesion for componentstrength. In a preferred aspect, the fiber guiding channels are formedat a depth that allows a portion of the fiber body to be positionedabove the top surface of the fiber guiding region.

The CFA base substrate sacrificial portion or region 329 also includesguiding channels, as the sacrificial portion or region 329 is separatedfrom the fiber guiding region 326 by one or more “snap-gap” channelsthat are formed transverse to the direction of the fiber guidingchannels. In FIG. 3A, one snap gap 328 is shown in the in-process CFAstructure 300, although more than one snap gap can be formed in thebase. The sacrificial portion or region 329 supports the aligned fibersduring the grinding/polishing procedures and protects the fibers untilthey are “released.” Thus, the sacrificial portion or region 329 canreduce the likelihood that fibers may chip and/or break during thegrinding/polishing process. In addition, sacrificial portion or region329 can be used to increase the likelihood that the fiber end-faces areoptically clear and all of the fibers are essentially the same length(within sub-micron tolerances) and with the same structure. Thesacrificial portion or region 329 also provides lateral supportpreventing the fibers from moving sideways as well as forward and backduring grinding and polishing and other component movement.

The CFA base substrate “snap-gap” 328 includes at least one channel orslot formed transversely to the fiber alignment channels. The “snap-gap”also separates the fiber guiding region and the sacrificial portion orregion. The snap-gap channel or slot 328 can be formed via etching atthe same time the fiber guiding channels are formed. Alternatively, thesnap-gap channel or slot 328 can be formed by cutting into a top surfaceof the base substrate 320 using a cutting tool, such as a diamond dicingsaw, when the base substrates are cut into strips containing multipleCFAs, as described further below.

The “snap-gap” 328 also can limit or stop the capillary flow of thebonding adhesive into the base substrate's sacrificial portion or region329. Any adhesive between the cover and the sacrificial portion orregion of the base substrate can bond the cover and base componentstogether, making it very difficult, if not impossible, to release thefibers after singulation. Further, the “snap-gap” 328 can provide amechanism to break-off the sacrificial portion or region to release thefibers, releasing the fibers to a cantilevered state and thus providinga straightforward way to seat the cantilevered fiber portions into theguiding grooves of a PLC during attachment, as described below. In anexemplary embodiment, the snap-gap 328 is etched or cut in a v-shape,thus providing a single stress point during the release step, andproviding an angled end face for the fiber guiding region 326 of thebase substrate 320 of the completed CFA. Snap gaps can also be formed assquare shaped or other shaped channels.

For example, FIG. 3B shows a top view of three different experimental SiCFA base substrates. These bases have been singulated to an appropriatewidth for one-at-a-time CFA assembly (in practical applications,finished CFAs can be diced closer to the fibers/v-grooves). Allexperimental CFA base substrates have eight v-grooves and have differentoverall lengths: 5 mm, 7.5 mm and 12 mm (top to bottom respectively).The center base has an etched snap-gap and the top and bottom bases (asshown in the figure) have snap-gaps cut using a dicing saw.

Also in step 404, the cover substrate(s) (if utilized in the finishedCFA) can be manufactured. An exemplary cover 330 is shown in FIG. 3A. Inan exemplary embodiment, the CFA cover 330 clamps the stripped opticalfibers into the channels or v-grooves in the sacrificial portion orregion of the base during the fiber grinding/polishing manufacturingoperation described below. In addition, the cover can protect theoptical fibers from excessive motion during the dicing process. Thecover also can press the cantilevered fibers into the v-grooves duringCFA assembly and CFA/PLC attachment. The cover can also provide somesupport to the optical fiber/PLC interface.

During the manufacturing process, for example, multiple cover substratescan be cut into strips of multiple arrays wide to match the basesubstrate width. Depending on the tooling used, the cover strip may becut slightly longer than the base substrates strip, as a longer coverstrip can be used to contact alignment equipment to properly set thecover position relative to the base substrate. Exemplary coverthicknesses can range from about 500 μm to about 1500 μm (or greater),depending on the rigidity required for a particular application,although other cover thicknesses can be utilized, as is practical. Forexample, a cover 330 with increased thickness can increase the strengthof the CFA/PLC gap fiber support. In addition, an increased fused silicacover thickness can increase the strength of a component in the systemwith the same mechanical, thermal characteristics as the fiber(s).Further, the cover's stiffness increases with thickness, thus decreasingcover flexing during the bonding process.

Cover 330 can have a substantially planar or flat inner surface (i.e.,the surface in contact with the base substrate) or the inner surface caninclude guiding channels that correspond to the guiding channels in thebase substrate. In a further alternative aspect, cover 330 can beconfigured to include a fiber support region, similar to that describedabove. In an exemplary embodiment, cover 330 has a flat inner surface,as a flat cover is less expensive to produce. In addition, thecross-section of a flat cover substrate covering a fiber seated in av-groove reduces the amount of void area surrounding the fiber, whichreduces the amount of adhesive that can surround the fiber afterbonding. Excessive adhesive surrounding the seated fiber can affectoptical performance.

As with the base substrate, the cover 330 can include a snap-gap orchannel 338. Similar to the base snap-gap(s), the CFA cover “snap-gap”338 includes at least one channel or slot formed transversely to thefiber alignment channels of the base, and can separate a main coverregion 336 from a cover sacrificial portion or region 339. The snap-gapchannel or slot 338 can be formed via etching or by the use of a cuttingtool, such as a diamond saw.

In addition, depending on the CFA configuration, the edges of the cover330 can be chamfered to provide a low-stress lead-in for the fiber. Thechamfering of the cover's edges can be cut into the cover during theformation of the cover snap-gap(s). Alternatively, the cover chamfer canbe ground on the edge after the dicing step. Chamfering of the cover inthe context of this application involves radiusing the edge of the coverto prevent direct contact of the bare fiber with a sharp edge of thecover. In an exemplary aspect, the back edge of the cover is chamferedin the vicinity of the strain relief region prior to the assembly of theCFA.

The “snap-gap” 338 also can limit or stop the capillary flow of thebonding adhesive onto the cover's sacrificial portion or region 339. Asmentioned above, any adhesive between the cover and the sacrificialportion or region of the base substrate can bond the cover and basecomponents together, making it very difficult to release the fibersafter singulation. Further, the “snap-gap” 338 can provide a mechanismto break-off the sacrificial portion or region 339 to release thefibers, in some embodiments. In an exemplary embodiment, the snap-gap338 is etched or cut in a v-shape, thus providing a single stress pointduring the release step. According to various embodiments, the coversnap-gap 338 can be located at the same location along the fibers as thebase snap-gap 328, or at a different location along the length of thefibers.

The base substrate and cover can be cleaned prior to step 406 in orderto remove debris. For example, the guiding or v-groove substrates can becleaned and inspected to insure the removal of particles and anychemical contamination. Cleaning can be accomplished by using a seriesof dips in solutions, such as detergent/deionized water/acetone/HFEsolutions, that are ultrasonically agitated. Visual inspection can beused to confirm the presence/absence of debris or other contaminants.

Referring back to FIG. 4, in step 406 fiber alignment is performed. Inone exemplary embodiment, the fibers can be aligned by placing thestripped fiber end(s) into the fiber guiding channels of the basesubstrate. Once all of the fibers of an individual cable are properlypositioned in the guiding channels, the fiber cable can be clamped intoposition. The fiber cables can be aligned and clamped one-by-one to fillall the fiber channel sets on the base substrate. Further alignment canbe performed by setting the appropriate fiber cable jacket/basesubstrate strain-relief region overlap such that the end of the fibercable jacket is roughly centered in the strain-relief region.

In step 408, a cover alignment to the fiber filled base substrate isperformed. In one exemplary embodiment, the snap-gap 338 in the covercan be aligned to the snap-gap 328 in the base substrate. The base andcover can be held in place by, e.g., clamps, vacuum chucks, etc., thenbrought into contact with each other. In order to avoid potentialmisalignment of the fibers, the cover is held such that the innersurface of the cover is substantially parallel to the fiber guidingsurface of the base. Once the cover is properly positioned, the bondhead is lowered to clamp the base, fiber, cover assembly together.

In step 410 bonding is performed. In one exemplary embodiment, bondingis accomplished by dispensing a structural adhesive, such as a thermallycurable adhesive, on the strain-relief region 325 of the base. Clampingthe fibers between the base 320 and the cover 330 before the adhesive isapplied can result in a 3-point line contact between each fiber and thebase and the cover. Capillary action will cause the adhesive to flowalong the fibers/v-grooves and between the cover and base substrate. Thecapillary force will diminish at the collective opening of thecover/base snap-gaps and the adhesive flow can stop. The adhesive curingprofile is adhesive dependent. Exemplary adhesives include 3M DP-190Scotch-Weld adhesive, available from 3M Company, St. Paul, Minn., wherethis adhesive is a thermally accelerated curing structural 2-part epoxy.As mentioned previously, other adhesives can be utilized.

In addition, in an exemplary embodiment, the fiber aligning grooves inthe base substrate can be designed to minimize the amount of structuraladhesive that collects in the immediate vicinity of the fiber, as atleast some polymeric adhesives can affect the light propagation withinthe fiber when in use. Also, excessive adhesive shrinkage during curingcoupled with a high modulus adhesive can result in some longitudinalcompression of the optical fiber, which can cause micro-bend losseswithin the fiber. To that end, the center-to-center spacing and theshape/type of channels or v-grooves in the fiber guiding region can be afactor in the amount of structural adhesive near the fiber(s).

In step 412, grinding and/or polishing is performed on the terminal endof the in-process CFA 300. In this step, the fiber terminal ends can bepolished in mass to provide flat-polished, wedge-polished,cone-polished, or angle-polished terminal ends.

In an exemplary embodiment, CFA 300 includes a cover 330 to protect thefibers during mass grinding/polishing. Allowing the fibers to flex backand forth during the grinding/polishing process could cause fiberbreakage, chipping or other damage. Further, with the cover 330 inplace, there is no need to temporarily bond the fibers into the channelsor v-grooves.

For example, grinding and polishing can be performed using aconventional polishing device, such as a modified Ultra-Tec Ultrapol®lapping/polishing system. Exemplary grinding and polishing equipmentmaintains polishing quality and surface flatness, e.g., by using anoscillating swing arm mechanism to simplify fiber cable management. Inexperiments conducted by the investigators, an oscillating swing-arm wasmodified to include an adjustable floating head mechanism while stillincorporating the angle adjustment features, to provide for verticalpolishing height adjustment when changing platens or lapping films. Theadjustable floating head can provide for the grinding/polish force to beeasily adjusted while maintaining the angular adjustment setting.

In addition, the use of an oscillating swing arm mechanism can helpmaintain the CFA assembly's orientation to the rotating platen.Maintaining the CFA orientation to the rotating platen allows the fibersto be continuously forced into the v-grooves, which minimizes possiblemovement of the fibers.

In an exemplary embodiment, during the grinding/polishing operation, thecover and base substrates are substantially prevented from flexing, asflexing of the cover or base substrates could allow the fibers to movein the guiding channels.

Flexing of the cover and base substrates can also result in the creationof space for debris to build up between the fiber and cover and basesubstrates. This debris can change the angle that the fiber(s) will bepolished, slightly deviating from the desired end-face angle. To helpminimize fiber movement in the guiding channels during polishing, theCFA assembly can be rigidly clamped as close to the finished end lengthas practical. For example, a mechanism can be integrated into the clampto fasten the clamp to the swing-arm assembly.

Exemplary grinding/polishing abrasive media can be utilized in step 412,such as 3M Diamond Lapping Films, available from 3M Company, St. Paul,Minn. Grinding is utilized to prepare the fibers to the proper length,while polishing is used to define the shape of the fiber terminal ends,and to remove pits formed in the grinding stage. In experiments, sampleCFAs underwent grinding and polishing (for approximately 30 seconds persheet) using progressively decreasing grit size abrasive sheets, from 30micron grit size continuing down to 15, 9.0, 6.0, and then 3.0-micronabrasive (for grinding), and 1.0, 0.5 and 0.1-micron abrasive grit sizefor polishing. The times stated in this example can vary with the numberof CFAs in a subassembly and the application specific size and width ofthe CFA components. As would be apparent to one of ordinary skill in theart given the present description, there are alternativegrinding/polishing implementations that can be utilized.

The above grinding/polishing step can be performed in mass; where all ofthe fibers of a single CFA or a CFA strip are ground and polished at thesame time, minimizing the fiber-to-fiber variation.

As described above, multiple CFAs can be configured, etched, assembledand ground/polished in batch form as a strip of one-to-many CFAs. Instep 414, singulation can be performed, where a strip of CFAs issingulated or diced into single individual CFAs. The timing of this stepis application specific. If multiple CFAs are attached to the samenumber of PLCs in batch form, singulation can be performed after theends are attached.

For singlewide attachments, the CFA strip can be sliced to proper widthusing a wafer dicing saw or other suitable cutting tool.

In step 416, the fiber is released from the base and/or cover substratesto form a cantilevered fiber. In an exemplary embodiment, releasing isperformed after singulation. In the releasing step 416, the sacrificialportion of the base and/or cover substrate is broken off exposing thecantilevered fiber. The releasing step can be performed by applyingappropriate force (e.g., by hand or by tool) to the sacrificial portionof the base/cover substrate. The direction of the applied force ispreferably transverse to the plane of the base/cover (e.g., a downwardforce can be applied to the base to release the base). The presence ofthe “snap-gap” allows the sacrificial portion to be broken off cleanly,as the “snap-gap forms a single stress point and prevents adhesive flowto the sacrificial regions of the cover/base substrates. Depending onthe type of structure desired for a particular application (see e.g.,the example structures shown in FIGS. 2A-2F), one or both of thebase/cover sacrificial regions can be released.

Also, with respect to the embodiments shown in FIGS. 2E and 2F, anadditional saw cut (227, 228) can be made to yield a fiber that isshorter than either the cover or base. Specifically, in the exemplaryembodiment of FIG. 2E, the CFA is cut from the bottom side of the basesuch that the blade of the dicing saw cuts through the base and fiberand into the cover to form a slot 227. After the slot has been formed,the remaining base sacrificial portion(s) can be released. A similarprocess can be used to manufacture a CFA in accordance with FIG. 2F,except that the saw cut is made through the cover and into the baseforming slot 228, followed by the release of the remaining coversacrificial portion.

In step 418, a cleaning step can be utilized. For example, if the CFA isto be attached to a PLC, cleaning can be the last operation prior toattachment. The grinding/polishing and dicing operations can create alarge amount of debris or contaminants that can inhibit the fibers fromfully seating into the PLC device's receiving grooves and prevent properlight propagation. For example, cleaning can be performed using a hotacid bath (e.g., sulfuric acid) to remove any excess structural adhesiveand a diluted potassium hydroxide bath to remove particulates.

In another embodiment, for mass production, whole silicon wafers can belaid-out with CFA substrates to maximize the number of arrays orpossibly match the center-to-center spacing of the waveguide devicesubstrates. In either case, the fiber arrays can be assembled,ground/polished and cleaned in mass, in a manner similar to thatdescribed above, to maximize manufacturing throughput.

Ultimately, the above process can be varied, as would be apparent to oneof ordinary skill in the art given the present description. For example,the layout of the array base substrate can designed to match the layoutof different PLC device configurations, including the number of channelsor v-grooves and the center-to-center spacing of the channels orv-grooves. As mentioned above, the number of channels or v-grooves foreach PLC can be from 1 to x, where x can be any number (limited only bythe width of the wafer).

In an alternative embodiment, as is shown in FIGS. 7A-7B, a CFA 600 canbe configured to combine the fibers of a plurality of fiber ribboncables. In this exemplary embodiment, two separate fiber ribbon cables610, 611 are utilized. For example, the fibers 612 and 614 of ribbons610 and 611 can be prepared, as described above. The ribbons 610 and 611can be arranged in a stacked arrangement (as shown), or in aside-by-side arrangement. The base substrate 620 can include a pluralityof fiber guides or channels 625, such as v-grooves, in which strippedportions of the fibers 612, 614 are disposed and guided. In thisexemplary embodiment, the fibers 612 and 614 are interleaved with oneanother and guided on fiber guides or channels 625. In addition, thecover 630 can include a channel or cut-out 638, which can stop the flowof adhesive when using an adhesive to bond the CFA to, e.g., a PLC.

As mentioned above, in one exemplary application, the CFAs describedabove can be coupled to a planar lightwave circuit (PLC). The circuitportion of the PLC is a planar waveguide circuit that can be configuredin a variety of ways, including, but not limited to, a straight linecircuit (1 to 1), a splitter circuit (1 to 2n), an arrayed waveguidegrating wavelength multiplexer, a thermo-optic switch, a microresonatorsensor array, and a cross connect-type circuit. Different types ofwaveguide patterns can be utilized for the PLC, as would be apparent toone of ordinary skill in the art given the present description.

FIG. 5 shows such an exemplary CFA-PLC structure, optical device 500,shown in side view. The two main components of device 500 are CFA 501and PLC 550. CFA 501 includes one or more fibers 510, such as from anoptical fiber cable, such as a fiber ribbon cable. Stripped portions ofthe fibers 511 are mounted on a base 520. The base 520 includes aplurality of fiber guides or channels, such as v-grooves, in whichstripped portions of the fibers 511 are disposed and guided. A cover 530can be optionally disposed on the substrate/guided fibers to preventfiber displacement within the channels or grooves and to provideadditional support when coupling to PLC 550. In addition, a structuraladhesive 540, such as a thermally accelerated curable structuraladhesive, (e.g., a two-part epoxy) can be provided to bond the fibers tothe base 520 and the channels or v-grooves, and to bond the cover 530 tothe base 520.

The base end face 523 (and/or the cover end face in other embodiments)can be formed at an angle, as a result from the release of a sacrificialportion during the releasing step described above. In addition, thecover 530 can include a channel or cut-out 538, which can stop the flowof adhesive. The structure and fabrication of CFA 501 can take place ina manner similar to that described above for CFA 100 and CFAs 200A-200F,such that the CFA may take one of many alternative forms. For example,in an alternative structure, the CFA orientation can be flipped over(such that the base is above the fiber and cover), such that the end ofthe base substrate extends beyond the end of the cover. In thisimplementation, the guide channels of the base substrate can provideboth vertical (up or down) and horizontal (side-to-side) support for thecantilevered fibers being coupled to the PLC.

The PLC 550 (described in greater detail with respect to FIG. 6 below)can include a waveguide substrate 560 that supports waveguide cores 570(waveguide cladding layer(s) are omitted from FIG. 5A for simplicity),which can be optically coupled to the output ends of the cantileveredfibers of the CFA. Waveguide substrate 560 further includes a pluralityof alignment features, such as fiber guides or channels, such asv-grooves, to receive and align the cantilevered fibers from the CFA.Index matching adhesive 580, such as UV curable index matching adhesive,can be used to bond the CFA to the PLC, although other types ofadhesives can also be utilized.

An example PLC, and an exemplary method of making a PLC, are describedin further detail in pending and commonly-owned U.S. Patent PublicationNo. 2005/0284181 A1, incorporated by reference herein in its entirety.As shown in FIG. 6, an exemplary PLC can include a planar waveguideassembly 20 having integral alignment features 22 for positioning anoptical fiber 24 (such as from a CFA). In this exemplary embodiment, thesingulated waveguide assembly comprises a substrate 26 having alignmentfeatures 22 formed therein. An etch stop layer 28 covers the substrate26. The etch stop layer 28 includes a patterned portion (hidden in FIG.6) corresponding to a pattern of alignment features 22. A waveguidestructure 32 is positioned on the etch stop layer 28, with only thepatterned portion of the etch stop layer 28 uncovered or revealed bywaveguide structure 32. The uncovered or revealed patterned portion ofthe etch stop layer 28 may optionally be removed after formation ofalignment features 22. A portion of the etch stop layer 28 remainspositioned between the substrate 26 and the waveguide structure 32, evenif the patterned portion is removed.

In an exemplary embodiment, the waveguide assembly comprises a siliconsubstrate 26 having a plurality of V-shaped (or other shaped) alignmentfeatures 22 formed therein. A silicon nitride etch stop layer 28 coversthe substrate 26 between substrate 26 and waveguide structure 32.Waveguide structure 32 includes a plurality of waveguide cores 40 (eachcorresponding to an alignment feature 22) sandwiched between a lowercladding layer 42 and an upper cladding layer 44.

In addition, PLC 20 further includes a transverse channel 50, such asformed by a saw cut or similar operation, formed at the junction of thewaveguide cores 40 and alignment features 22 to remove any residualradius at the junction and provide a flat surface at the end of thewaveguide cores 40 suitable for mating to an optical fiber or otheroptical device. The walls of the transverse channel 50 may beperpendicular to the wafer surface, or angled for reduction of opticalreflections. The channel formation can be performed during componentdicing operation. Strips of waveguide chips (not shown) are diced fromthe substrate 26, and the ends of the waveguide cores 40 may be given anadditional optical polishing treatment. The strips of waveguide chipscan be further diced to separate individual planar wave-guide assemblies20. The singulated assemblies are then ready for cleaning and assemblywith optical fibers from a CFA.

In one embodiment, the number of fiber receiving channels disposed inthe PLC substrate matches both the number of waveguide cores disposed inthe PLC and the number of fibers extending from the CFA. In analternative embodiment, the PLC substrate can include a greater numberof fiber receiving channels than the number of fibers extending from theCFA or waveguide cores disposed in the PLC. For example, due to possiblesymmetrical differences between the PLC channels and the CFA fiberchannels, there may be minor differences in the Si etch rate duringmanufacturing (for embodiments where the PLC substrate and the CFAsubstrate are both Si-based). In the event that the etching processesare not matching, providing extra fiber receiving channels in the PLCsubstrate can compensate for different etch rates. To maintain symmetry,the extra fiber receiving channels can be exact copies with the samecenter-to-center spacing and can be placed outwardly of the active fiberreceiving channels. Similarly, extra fiber guiding channels or v-groovescan be added to the CFA. In addition, dummy fibers can be used to fillnon-operative outer fiber channels.

As shown in FIG. 5B, in top view, the CFAs and PLCs may be produced inmass form, such as using non-diced CFA strips 501A and/or 501B, andnon-diced PLC strip 550. The strips can be diced (as described above) toform single CFA-PLC devices or CFA-PLC-CFA devices (where both ends ofthe PLC are coupled to CFAs).

The present description further provides a method for the accurate andrapid passive coupling of CFAs to PLCs. Passive alignment isadvantageous in that there is a reduced need for active equipment totransmit light through the source fibers and to detect and measure theoutput light amplitude. An inherent problem with an active method isthat only the light coupling of the active fiber channels is maximized,the other optical channels may have much lower output levels dependingon the individual fiber/waveguide lateral offset and the warp/curvatureof both the PLC wafer and the fiber array substrate creating an offset.In addition, an active coupling technique can require that an operatormanually adjust the initial position of the fiber arrays until at leasta small level of light coupling is achieved. In most cases, both theinput and output fiber(s) must be positioned and aligned whileattempting to achieve maximum light throughput which increases thecomplexity of the problem.

The use of a CFA, such as described above, decreases some of themechanical tolerances of the actual optical components while providingpassive optical alignment. The CFAs also decrease the precision andcomplexity of the alignment equipment, further decreasing themanufacturing costs. The cantilevered fibers of the CFAs described aboveare tolerant of the center-to-center spacing differences between theindividual PLC light paths.

In this exemplary embodiment, the alignment features 22, such asv-grooves, of the PLC device can set the horizontal and verticalposition of the cantilevered fibers. The CFAs are effectively immune tothe (non) flatness issues of the PLC or the fiber array substratesbecause the cantilevered fibers have the ability to “float” verticallyand horizontally to match the component's v-groove spacing, necessaryfor true passive alignment. This is also true with depth variations ofthe PLCs' alignment features; as the cantilevered fibers from the CFAcan conform to the PLCs' v-groove profile.

According to an embodiment of the present invention, a CFA is designedto be manually or automatically attached to a PLC device. As would beapparent to one of ordinary skill in the art given the presentdescription, while there are a number of different ways to orientate,align and bond the CFA to the PLC, this present example provides aone-at-a-time bonding method.

In this exemplary embodiment, a PLC is attached to a CFA using aconstant force bonder, where one of the PLC/CFA is initially heldstationary, while the other component is moved into place so that thecantilevered fibers of the CFA are received by the fiber receivingchannels of the PLC. In one example, the bonder can include a stationarythermode with an integrated vacuum chuck to hold the PLC device inplace. A bond head can be positioned above the thermode. The bond headcan be mounted on a vertically mobile x/y planarization stage. Thevertical stage can be motor driven with an air driven sub-stagecontrolling the bonding pressure. Prior to bonding, the bond headcontact surface can be adjusted parallel to the thermode using the x/yplanarization stage. The bond head can be constructed from quartz toallow the use of UV cured adhesives. The bond head can be designed tocontact only the CFA cover above the fiber receiving channels of thePLC. To allow for infinitesimal height differences in v-groove heights,the bond head can be coated with a very thin compliant layer (such asTeflon tape). The bonder can also include one or more microscopes forvisual inspection of the coupling.

During CFA/PLC attachment, an excessive cover width, in conjunction withthe bonding compliant layer, can result in a bending of the outwardedges of the cover downward. This bending moment can change the purelyvertical motion of the bond head to one with a vertical plus a slighthorizontal component. This horizontal force can cause lateralmisalignment to occur. In an exemplary embodiment, a thicker, narrow CFAcover can reduce the likelihood of this potential problem.

The CFA can be clamped in a multi-axis stage, for example a 5-axistranslation stage (e.g., x, y, z, pitch and yaw). The clamp holding theCFA can clamp on the CFA or on the fiber cable. A flexible cantileveredspring can be mounted on the clamp to apply a small amount of pressureto the top of the CFA. This spring preferably only contacts the CFA inthe strain-relief region, with the cantilevered fibers protruding outtowards the thermode. The spring can control the roll of the CFA, afurther degree of translation. The cantilevered spring also allows for alimited amount of vertical motion and pitch change during bondingwithout damaging the CFA or the PLC.

The pitch of the fibers can be adjusted (for example, to anapproximately 2° pitch) so that the tips of the fibers are oriented down(closer to the v-grooves). The fibers can be positioned over the PLCv-grooves and adjusted parallel and centered on the v-grooves. The endsof the fibers can then be positioned over the transverse channel (suchas channel 50, shown in FIG. 6) at the end of the waveguide/v-grooveinterface. Once parallel and centered, the fibers are lowered into thev-grooves until the cover/PLC gap is a minimum and parallel. To allowfor thermal expansion, the waveguide/fiber gap can be set to anappropriate amount (e.g., approximately 5 microns) by moving the fiberscloser to the PLC waveguides, preferably without touching the fiberterminal ends to the waveguide core.

The bond head can be centered and then lowered onto the CFA coverpressing the fibers into the v-grooves of the PLC device. Index matchingadhesive can be applied to the fiber/waveguide interface, which thenflows down the fiber/v-groove voids, filling the cover's snap-gap andthe CFA/PLC gap. Suitable adhesives are described in commonly-owned,co-pending U.S. patent application Ser. No. 11/423,191 (Attorney DocketNo. 61993US002), incorporated by reference herein in its entirety. Thus,the cantilevered optical fibers of the CFA are encapsulated andprotected by the CFA cover, PLC substrate and the adhesive(s) used. In apreferred aspect, as the cover can be manufactured from a fused silicaor quartz material, UV light can be applied through the cover toinitiate curing of a UV curing adhesive, followed by heat to finalizethe cure. On completion of the cure cycle, the heat is removed and theassembly is allowed to cool under-pressure. Alternatively, as describedbelow, a clamping method can be utilized to couple the CFA and PLC.

In the above bonding example, the CFAs are attached one-at-a-time. Withrelatively simple modifications to the bonder, CFAs can be attached toboth ends of the PLC as a single bond cycle. For double-ended bonding,an accommodation of the thermal expansion growth of the PLC during thethermode cure portion of the cycle can be taken into account.

As described above, the optical adhesive used to bond the CFA to the PLCcan be applied after the fibers are fully seated in the v-grooves andpositioned relative to the waveguide end-face. This procedure canprevent the need to squeeze the adhesive out of the way of the fiber, asadhesive lodged between the fibers and the v-groove walls can cause apositional offset, adversely affecting optical coupling.

A CFA-PLC device, such as described above, may be used in a wide arrayof applications including passive optical splitters, wavelengthmultiplexers, optical switches, polarization controllers, integratedoptical lasers and amplifiers, and optical sensors.

For example, FIG. 8 shows an exemplary PLC that is designed as anoptical sensor chip 650. The sensor chip 650 can include a waveguidesubstrate 660 that supports one of more waveguides 670, which can beoptically coupled to the output ends of the cantilevered fibers of theCFA. Waveguide substrate 660 further includes a plurality of alignmentfeatures, such as fiber guides or channels 665, such as v-grooves, toreceive and align the cantilevered fibers from the CFA. A transversechannel 668, such as formed by a saw cut or similar operation at thejunction of the waveguides and alignment features can be implemented toremove any residual radius at the junction and to provide a flat surfaceat the end of the waveguides suitable for mating to the CFA fibers. Inaddition, a sensor element can be incorporated on sensor chip 650. Inthis exemplary embodiment, a ring resonator 675 is disposed on chip 650to optically interact with one or more waveguides 670. For example,sensing can take place as is described in co-pending, commonly ownedU.S. patent application Ser. No. 11/277,770, incorporated by referenceherein in its entirety.

In some applications, permanent bonding of the CFA to the PLC may not bedesired. For example, many telecommunications components must be housedin protective enclosures that shield them from mechanical orenvironmental damage. These components typically have permanent fibercable lengths, or “pigtails” attached to them, which are spliced toother fibers to complete the optical circuit. This results in excessfiber cable lengths, which are coiled and stored in the enclosure, oftencreating the need for additional space for excess fiber length storage.It is therefore desirable to have PLC components with optical connectorinterfaces integrated in the PLC package, rather than pigtails. As isapparent from the description herein, if the PLC package is providedwith a retention mechanism to hold the CFA fibers in registration withthe PLC alignment grooves, a connectorized interface suitable formultiple connection-disconnection cycles can be achieved. A schematicdrawing of an exemplary connector interface is shown with respect toFIGS. 9-11E.

As shown in FIG. 9, the CFA-PLC device can be configured as a plug andsocket connection system. In particular, device 700 can include a CFAplug element 701 that is configured to be received by PLC socket orreceptacle element 750 as a releasable connection.

In particular, as is shown in greater detail in FIGS. 10A and 10B, CFAplug element 701 includes a CFA 705, which can be configured andmanufactured in a manner similar to that described above. In thisexemplary embodiment, CFA 705 can be configured in a manner such as CFA501 shown in FIG. 5A, and described above. In this exemplary embodiment,CFA 705 can include a plurality of prepared fiber ends 712 from a fiberribbon cable 710. The fibers can be mounted to a CFA base substrate 720.A cover 730 can protect the cantilevered fibers.

CFA plug element 701 can include a cover portion 745 and a base portion740. The base and cover portions can be injection molded and shaped tobe received by PLC socket element 750. Further, cover portion 745 canfurther include guide pins or protrusions 747 that can engage withreceiving/guiding channels 759 formed in PLC socket 750. CFA 705, inparticular cover 730, which can be used as a reference surface, can bebonded onto a surface 746 of cover portion 745. Optionally, the fiberribbon cable 710 can also be bonded to a surface of cover portion 745.The base portion 740 provides a support surface 742 for CFA basesubstrate 720 and can be bonded to cover portion 745 to complete theplug portion.

The CFA plug 701 can be releasably connected to a PLC socket orreceptacle structure 750 as shown in the connection sequence of FIGS.11A-11E. In this embodiment, the CFA is not required to be bonded to thePLC in order to achieve suitable coupling.

FIG. 11A shows a side view of device 700, which includes CFA plug 701and PLC socket or receptacle 750. PLC socket 750 includes a socket body751 formed from an injection molded material. The PLC socket 750 furtherincludes a waveguide die carrier 782 which supports the PLC waveguidedie 752 mounted thereon, such as PLC 650 described above, and ismoveable within PLC socket 750. In this example, a PLC socket retainerportion 757 can provide a spring/compression force onto PLC waveguidedie 752 to keep it in place on moveable die carrier 782. PLC socket 750further includes a latch 785, used to complete the connection process.In FIGS. 11A-11D, latch 785 is shown in its insert position. PLC socket750 further includes a locking mechanism or retainer portion 755 thatretains the CFA plug 701 in opening 758. PLC socket 750 also includes anopening 753 which allows the user access to a surface of the PLC fortesting and analysis. In this regard, if fluids are placed on PLCwaveguide die 752 for testing, the PLC socket retainer portion 757 canbe configured to prevent flow of the fluid towards the CFA fibers towhich the PLC is connected.

As shown in FIG. 11B, the CFA plug 701 can be inserted in PLC socket 750through opening 758. The retainer portion 755 can be flexed out of thepath of CFA plug 701. FIG. 11C shows the CFA plug 701 inserted about 75%of the way in the PLC socket. As shown in FIG. 11D, the CFA plug 701 isabout 100% inserted into PLC socket 750. The CFA retainer portion 755flexes back to its normal state and prevents CFA plug 701 from slidingout of the socket 750. In addition, a portion of the PLC socket body,shown in FIG. 11D as portion 756 applies a downward force to the CFAcover portion 745, forcing the cantilevered fibers into the receivinggrooves of the PLC substrate. The receiving grooves can optionallyinclude an index matching fluid.

In an exemplary embodiment, the waveguides are brought into more optimaloptical coupling with the fibers of the CFA by further moving the PLCdie towards the locked in fibers of the CFA. As shown in FIG. 11E, latch785 can be rotated in the direction of arrow 789. As latch 785 moves, aportion of die carrier 782 is engaged by projection 786 which pushes diecarrier 782 towards the terminal ends of the CFA fibers. The latch 785can be temporarily locked in place after rotation by a lockingmechanism, such as a detent (not shown). Thus, a mechanical system, asopposed to a bonding material, can complete the connection of the CFAfibers to the waveguides of the PLC. In addition, the CFA plug portioncan be removed from PLC socket 750 by releasing the retainer portion 755and sliding the plug 701 out of the PLC opening 758.

As described above, the PLC can be configured as part of a sensingdevice that performs optical sensing. The sensor may be a one-use devicefor performing a medical test on bodily fluids. In this exemplaryembodiment, the sensor chip can be designed to be discarded after oneuse. In the above example, the PLC die 752 is retained by compressionforces, as opposed to permanent bonding. Thus, the CFA can beincorporated into the readout system as a temporary optical interfacebetween the disposable PLC chip and the more expensive opticalcomponents (e.g. laser source, spectrometer, power meter, etc)comprising the readout system.

Although specific embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent implementations calculated to achieve thesame purposes may be substituted for the specific embodiments shown anddescribed without departing from the scope of the present invention.Those with skill in the mechanical, electrical, chemical and opticalarts will readily appreciate that the present invention may beimplemented in a very wide variety of embodiments. This application isintended to cover any adaptations or variations of the preferredembodiments discussed herein.

1. A fiber alignment device, comprising: a base having at least onealignment groove; a stripped portion of an optical fiber positioned inthe at least one alignment groove; and a cover, wherein a terminal endof the fiber extends beyond at least one of an end face of the base andan end face of the cover, wherein the cover is bonded to the base tosecure the optical fiber between the base and the cover, wherein an endface of the cover and the end face of the base are substantiallynon-parallel.
 2. The fiber alignment device of claim 1, wherein theterminal end of the fiber extends beyond the end face of the base. 3.The fiber alignment device of claim 1, wherein the fiber alignmentdevice is configured so that the cover end face extends beyond the endface of the base.
 4. The fiber alignment device of claim 1, wherein thebase end face extends beyond the end face of the cover.
 5. The fiberalignment device of claim 1, wherein at least one of the cover and thebase further includes a support region to support a non-stripped portionof the fiber.
 6. The fiber alignment device of claim 1, wherein the basefurther includes a plurality of alignment grooves spaced apartsubstantially in parallel to receive a plurality of optical fibers. 7.The fiber alignment device of claim 1, wherein at least one of the coverand the base includes a channel formed in a direction transverse to theat least one alignment groove.
 8. The fiber alignment device of claim 1,wherein the base comprises one of silicon, quartz, and borosilicateglass.
 9. The fiber alignment device of claim 1, wherein the covercomprises fused silica.
 10. The fiber alignment device of claim 1,wherein the end face of the cover is proximate to the end face of thefiber.
 11. An in-process structure for a fiber alignment device,comprising: a base having at least one alignment groove; a strippedportion of an optical fiber positioned in the at least one alignmentgroove having a terminal end; and a cover bonded to the base securingthe optical fiber between the base and the cover, wherein at least oneof the cover and the base has at least one transverse channel, orientedtransverse to the at least one alignment groove, and where at least oneof the cover and the base has at least one sacrificial region.
 12. Thein-process structure of claim 11, wherein the transverse channelprevents the flow of an adhesive disposed between the cover and thebase.
 13. The in-process structure of claim 11, wherein the base furtherincludes a plurality of alignment grooves spaced apart substantially inparallel to receive a plurality of optical fibers.
 14. The in-processstructure of claim 11, wherein a body portion of the fiber extends abovethe first surface of the base when the at least one fiber is positionedin the alignment groove.
 15. The in-process structure of claim 11,wherein the surface of the cover disposed on the positioned fiberincludes at least one alignment groove.
 16. A method of forming a fiberalignment device, comprising: providing a base having at least onealignment groove formed in a first surface thereof; providing a cover;forming a transverse channel, oriented transverse to the at least onealignment groove, in at least one of the first surface of the base and afirst surface of the cover; placing a stripped potion of an opticalfiber in the at least one alignment groove; bonding the cover to thebase to secure the optical fiber between the first surface of the baseand the first surface of the cover; and releasing a portion of at leastone of the base and the cover at the transverse channel.
 17. The methodof claim 16, further comprising polishing a terminal end of the opticalfiber prior to the releasing step.
 18. The method of claim 16, whereinafter the releasing step, a terminal end of the optical fiber extendsbeyond at least one of an end face of the cover and an end face of thebase.
 19. The method of claim 16, wherein the releasing step comprisesapplying a force to at least one of a sacrificial region of the base anda sacrificial region of the cover, wherein the direction of the force istransverse to at least one of the plane of the base and the plane of thecover.
 20. A method of forming a plurality of fiber alignment devices,comprising: providing a base having an array of base portions, whereineach of the base portions has at least one alignment groove on a firstsurface of the base; forming a transverse channel in the base, where thetransverse channel is oriented transverse to the at least one alignmentgroove; placing a stripped potion of an optical fiber in the at leastone alignment groove in each of the base portions; bonding a cover onthe top surface of the base substrate to secure the at least one opticalfiber between the base and the cover; singulating the base to form thealignment devices; and removing a sacrificial portion of at least one ofthe base and the cover.
 21. A method of forming a fiber alignmentdevice, comprising: preparing an optical fiber cable that includes aplurality of fibers, wherein the preparing step comprises at least oneof coiling, stripping and cleaving one or more of the fibers of theoptical fiber cable; preparing a base to receive the prepared opticalfiber, wherein the preparing step further includes forming a pluralityof alignment grooves on a first surface of the base; providing a cover,wherein the cover includes a substantially planar inner surface and atransverse channel formed in the substantially planar inner surface;placing the prepared optical fibers in the alignment grooves; andbonding the cover on the top surface of the base substrate to secure theprepared optical fibers between the base and the cover.